1. Technical Field
The present invention relates to an electrophotographic toner and an electrophotographic developer that can be used in an electrophotographic device that uses an electrophotographic process, such as a copying machine, printer, or facsimile, and also relates to an image forming method.
2. Related Art
Generally, a fixed image is formed via multiple steps, including electrically forming a latent image, using any of a variety of techniques, on the surface of a photoreceptor (latent image holding member) that uses a photoconductive material, developing the thus formed latent image using an electrophotographic toner (hereafter also abbreviated as simply “toner”), thereby forming a toner image, subsequently transferring this toner image on the surface of the photoreceptor, either via an intermediate transfer material or directly, to the surface of a recording target material such as a sheet of paper, and fixing the transferred image by heating, pressure application, heated pressure application, or a solvent vapor method. Any residual toner on the photoreceptor surface is then cleaned as necessary, using any of a variety of methods, and the photoreceptor is then supplied for reuse within the above multiple of steps.
A typical technique for fixing the toner image that has been transferred to the surface of the recording target material is the heat roller fixing method, wherein the transfer target to which the toner image has been transferred is passed between a pair of either heated rollers or pressure rollers, thereby fixing the image. Furthermore, another similar fixing method, in which either one, or both of the rollers are replaced with belts, is also known. Compared with other fixing methods, these techniques yield a robust fixed image at greater speed, meaning they offer a higher level of energy efficiency, and they also generate minimal environmental impact resulting from volatilization of solvents or the like.
On the other hand, techniques that enable fixing to be conducted at lower energy levels are desirable in terms of reducing the energy consumption of printers. Accordingly, there is strong demand for electrophotographic toners capable of low-temperature fixing.
Typical techniques for lowering the toner fixing temperature involve lowering the glass transition point of the toner resin (the binder resin). However, if the glass transition point is lowered too far, then aggregation of the toner powder (blocking) becomes increasingly likely, and the storage properties of the toner at the surface of the fixed image deteriorate, meaning from a practical viewpoint, the lower limit for the glass transition point is 50° C. This glass transition point has been used as a specific design feature within many of the currently available toner resins, meaning producing a toner with better low-temperature fixability than conventional toners simply by lowering the glass transition point is no longer possible. Furthermore, the fixing temperature can also be lowered by using a plasticizer, but this generates problems in that blocking occurs during storage of the toner, or even within the developing unit.
The present invention provides an electrophotographic toner, an electrophotographic developer and a film forming method that are capable of realizing low-temperature fixing, are resistant to blocking, and are unlikely to suffer filming on the photoreceptor.